store emails in textfile? php

This spinet of code renders a users email when a user enters a page of my site: . .

$email=$userprofile->email;

. . you can echo it like this:

&l开发者_StackOverflow中文版t;?php echo $email;?>

but how would you store it in a text file with one email per line? thanks

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file_put_contents("name_of_file.txt", preg_replace("/\r|\n/"," ", $email)."\n");

Learn to use the php docs. They are excellent.